Abstract:

【Objective】 The purpose of this experiment was to breed new polyploidy varieties of leafy and fruit-producing mulberry for its diverse utilization, improve economic profit and study the effects of different ploidy on the photosynthetic characteristics of mulberry,thus providing a theoretical basis for its breeding. 【Method】 Individual excellent selection associated with chemical induction were adopted. The morphological characters, daily changes of photosynthetic rate and chlorophyll content were measured and ultrastructural changes of chloroplasts were observed. 【Result】 Results of three regional experiments showed that fruits yield of new variety was 45.8% higher than the control cultivar Hongguo2 and the mean leaves yield were 40% and 13% higher than the control cultivars ‘Hongguo2’ and ‘Husang 32’, respectively. The results of rearing silkworm showed that cocoon crop per 10 000 four-instar silkworm, cocoon shell weight per 10 000 four-instar silkworm and cocoon crop per 100 kg leaves were higher than only leave-producing control cultivar Husang32, increased by 4.65%, 4.35%, and 5.2%, respectively. This variety was registered and released for commercial production in Chongqing in 2009. Compared to clonal diploidy parent, synthetic character performance of tetraploid was superer and net photosynthetic rate and chlorophyll content increased, the number of the thylakoid per granum increased and the granum thylakoid piled up loosely and arranged orderly．【Conclusion】 The increase of number of the somatic chromosome of mulberry would in favor of the enhancement of leaf photosynthetic capacity and the new polyploidy variety of leafy and fruit-producing mulberry could not only increase the yield and quality of leaves, but also increase the yield and quality of fruits.

Key words: mulberry, polyploid, photosynthetic rate, ultrastructural chloroplasts